JP2002265906A - Adhesive composition for lamination used in flexible printed circuit board and adhesive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition for lamination used in a flexible printed circuit board that has excellent thermal impact resistance and press workability, and an adhesive film. SOLUTION: This adhesive film is composed of an adhesive composition for lamination used in a flexible printed circuit board comprising (a) an acrylic rubber having a carboxylic acid functional group, (b) an epoxy resin, (c) a polyamide amine, (d) a phenol resin, and (e) a curing agent or curing catalyst, wherein the added amount of component (c) is 0.1-10 pts.wt. per 100 pts.wt. of component (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board (hereinafter referred to as FP) having excellent thermal shock resistance and press workability.
The present invention relates to a laminating adhesive composition and an adhesive film for C).

[0002]

2. Description of the Related Art In recent years, demands for high-performance and high-density FPCs have increased the demand for multilayer FPCs having four or more layers. The multilayer FPC is obtained by laminating two or more single-sided or double-sided FPCs using an adhesive film to obtain a structure of four or more layers. The adhesive film used at this time has FPC in addition to adhesiveness, solder heat resistance and electrical insulation.
Press workability at the time of manufacturing and thermal shock resistance that can be insulated from thermal shock are required.

Conventionally, acrylonitrile-butadiene rubber-based, polyimide-based, epoxy resin-based, and acrylic rubber-based adhesives have been used as adhesives for FPCs. However, the acrylonitrile-butadiene rubber-based adhesive has a disadvantage that characteristics such as electric resistance and adhesive strength are likely to be reduced due to thermal deterioration.

In the case of polyimide, since the organic solvent used for the adhesive is a high-boiling solvent such as N-methylpyrrolidone, a large amount of the high-boiling solvent tends to remain as a residual solvent, and the solder heat resistance is reduced. It has the disadvantage of being easy. Epoxy resin adhesives are inferior in flexibility and have low adhesive strength.

Acrylic rubber-based adhesives soluble in low-boiling general-purpose solvents are excellent in heat deterioration resistance, drying properties, flexibility and adhesion, but are cured with a crosslinking agent such as isocyanate or melamine. If they are used alone, they have the disadvantages that the crosslinking density is lower than that of the epoxy-based and polyimide-based materials, sufficient electrical resistance cannot be obtained, and the migration property is poor. For this reason, a method of improving these characteristics by blending a thermosetting resin such as an epoxy resin with an acrylic rubber has been adopted. However, the solder heat resistance is insufficient or the amount of the adhesive flowing out during the pressing operation. There are many problems. In addition, when these adhesive films are used for a highly multilayered FPC, problems such as generation of cracks between layers due to inability to absorb the stress have been surfaced.

[0006]

In recent years, the manufacturing process of the FPC has been required to be finer and to have high pressability. That is, when the punched adhesive film is overlapped with the FPC and pressed, the problem that the amount of the adhesive flowing out to the punched portion is large has been emphasized more than before. In addition, the number of layers has been rapidly increasing, such as a conventional four-layer FPC having six or eight layers.

[0007] The fluidity in the B-stage state (semi-cured state) is greatly related to the press workability of the adhesive film.
If the fluidity is too large, the melted adhesive will flow into the punched portion of the FPC, impairing the reliability of the product. If the fluidity is too small, the adhesiveness to the adherend will be poor, and the adhesiveness and solder heat resistance will decrease. I do.

The adhesive film can be obtained by applying an adhesive composition dissolved in an organic solvent on release paper by using a roll coater or the like and drying it with a hot-air drier. The B-stage state in which the reaction has progressed due to the heat of the dryer. Usually, it is the adhesive film in the B-stage state that requires workability, and it has been strongly desired to improve the flowability during the FPC press work.

Further, the adhesive film has a multilayer F of 6 or more layers.
When used in a PC, there is a problem that the layers cannot be tolerated by stress in the thermal shock test, peel off between the layers, cracks occur in the through-hole plating, and the wires break.

[0010] These cracks disperse stress by lowering the elastic modulus of the adhesive, for example, by reducing the amount of filler,
Although it can be reduced, the fluidity of the B stage also changes at the same time, which worsens the flow during pressing. In addition, in order to reduce the influence on the outflow property in the B stage, it is also attempted to reduce the amount of a curing agent or a curing catalyst that hardly reacts in the B stage for the purpose of lowering the final crosslink density. Insufficient cure causes new problems such as a decrease in solder heat resistance, and it is difficult to balance thermal shock resistance with flow during pressing, and these solutions have been strongly desired.

[0011]

As a result of intensive studies to solve these problems, the use of a polyamidoamine, which can cure epoxy at room temperature, allows the adhesive film to flow out during press work. It has been found that the elastic modulus after final curing is lowered by controlling the molecular weight of the polyamide resin and incorporating a flexible molecular skeleton of polyamidoamine, thereby completing the present invention. That is, the present invention provides an FPC lamination comprising a carboxyl group-containing acrylic rubber (a), an epoxy resin (b), a polyamidoamine (c), a phenol resin (d), a curing agent or a curing catalyst (e). The present invention relates to an adhesive composition and an adhesive film for FPC lamination using the adhesive composition.

The carboxyl group-containing acrylic rubber used in the present invention is mainly composed of an alkyl acrylate (including a methacrylate, the same applies hereinafter), a vinyl monomer having a carboxyl group, and optionally a carboxyl group. It is a copolymer containing acrylonitrile, styrene and the like. Examples of the alkyl acrylate include ethyl acrylate (including ethyl methacrylate, the same applies hereinafter), ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, acrylic acid 2 Monomers such as ethylhexyl, undecyl acrylate, lauryl acrylate, and
Monomers having a hydroxyl group such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and allyl alcohol are exemplified. One or more of these can be selected and used. Examples of the vinyl monomer having a carboxyl group include, but are not limited to, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, and maleic anhydride.

The method of polymerizing the acrylic rubber is not particularly limited, and a general suspension polymerization method can be used. Examples thereof include a dispersant such as PVA, azobisisobutyronitrile (AIBN), and lauryl. Peroxide (L
A mixture of two or more of the above acrylic monomers is dropped into a liquid in which a polymerization initiator such as PO) is dispersed in an aqueous medium, and polymerized. The polymer is washed with purified water to remove impurities, washed with water and dried by heating to remove residual monomers and moisture. The number average molecular weight of the polymer is preferably about 50,000 to 500,000.

The epoxy resin used in the present invention includes compounds having two or more epoxy groups in the molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, Cresol novolak type epoxy resin, bisphenol A novolak type epoxy resin, bisphenol F novolak type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ester type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, Diglycidyl ether compounds of bifunctional phenols, diglycidyl ether compounds of bifunctional alcohols, and halides and hydrogenated products thereof can be used. These compounds are
They can be used alone or in combination of two or more. The amount of the epoxy resin is preferably in the range of 10 to 100 parts by weight based on 100 parts by weight of the acrylic rubber. 1
If the amount is less than 0 parts by weight, sufficient heat resistance cannot be obtained.

The polyamidoamine of the present invention is not particularly limited as long as it has a polyamide structure in the skeleton and at least two or more primary amino groups in one molecule. The addition amount is preferably from 0.1 to 10 parts by weight, based on 100 parts by weight of the epoxy resin. If the amount is less than 0.1 part by weight, the amount of the flow-out is large and the appearance of the product is impaired. Since the reaction in the B stage progresses too much, the adhesion to the adherend is reduced, causing problems such as blistering during pressing or curing.
Polyamidoamine can be mixed with other compounds in advance, but in order to improve the stability of the adhesive solution,
Mixing may be performed immediately before coating.

The phenolic resin of the present invention is not particularly limited as long as it is a thermosetting type.

The curing agent and curing catalyst of the present invention are curing agents and curing catalysts for epoxy resins and phenolic resins. For example, aromatic polyamines, amine complexes of boron trifluoride such as boron trifluoride triethylamine complex, imidazole derivatives such as 2-alkyl-4-methylimidazole and 2-phenyl-4-alkylimidazole, phthalic anhydride, trianhydride Organic acids such as melitic acid, dicyandiamide, triphenylphosphine, diazabicycloundecene, and hydrazine can be used. These curing agents and curing accelerators may be used alone, or two or more of them may be used in combination as needed. The addition amount is preferably 0.01 to 10 parts by weight based on 100 parts of the epoxy resin.
If the amount is less than 0.01 part by weight, complete curing of the epoxy resin cannot be obtained, and the solder heat resistance and the like are reduced. If the amount is more than 10 parts by weight, problems such as reduced adhesiveness and reduced storage stability occur. . In order to improve the storage stability in the B stage, it is preferable that the reaction hardly progresses in a normal temperature range.

In addition, a filler may be added to the adhesive as required. As the filler, any material having a higher elastic modulus than the resin and having an electrical insulating property can be used.For example, aluminum hydroxide, magnesium hydroxide, talc, alumina, magnesia, silica, titanium dioxide, silicic acid Powder fillers such as calcium, aluminum silicate, calcium carbonate, clay, silicon nitride, silicon carbide, aluminum borate, synthetic mica, and short fiber fillers such as glass, asbestos, rock wool, and aramid. ,
Whisker such as silicon carbide, alumina, aluminum borate and the like can be used.

These components are used after being dissolved or dispersed in an organic solvent such as methyl ethyl ketone, toluene, methanol, N-methylpyrrolidone, N, N-dimethylformamide.

When a filler is added, the particle size is adjusted to 10 μm or less using a ball mill or the like. When the thickness is 10 μm or more, unevenness is generated on the film surface when the adhesive film is formed, and the adhesiveness, the solder heat resistance is reduced, and the appearance is impaired.

The release paper used in the present invention is not particularly limited. For example, clay, kraft paper, roll paper, glassine paper, etc.
A coating layer of a filler such as polyethylene or polypropylene is provided, and a silicone-based, fluorine-based, or alkyd-based release agent is further applied on each coating layer, and polyethylene, polypropylene, ethylene-α- Olefin copolymers, various olefin films such as propylene-α-olefin copolymers alone, and those obtained by coating the release agent on a film such as polyethylene terephthalate may be mentioned. Use of alkyd-based release agent on both sides of high-quality paper and alkyd-based release agent, and polyethylene terephthalate for alkyd-based release agent, because mold force and silicone adversely affect electrical characteristics. Are preferred.

The adhesive film is obtained by directly coating an adhesive solution on release paper and drying the organic solvent. The coating method is not particularly limited,
A comma coater, a reverse roll coater and the like can be mentioned. The thickness of the adhesive film after drying is appropriately changed as necessary, but is preferably in the range of 3 to 200 μm.
When the thickness of the adhesive film is less than 3 μm, the reliability of interlayer insulation is reduced. When the thickness is 200 μm or more, there is a problem that drying is insufficient and residual solvent is increased, and blisters occur during pressing in FPC production. The drying conditions are not particularly limited, but the residual solvent ratio after drying is preferably 1% or less. If it is 1% or more, there is a problem that the residual solvent foams at the time of FPC pressing and causes blistering.

[0023]

Next, examples of the present invention and comparative examples will be described.

(Example 1) (1) Preparation of Adhesive Solution 100 parts by weight of a carboxyl group-containing acrylic rubber WS023DR (manufactured by Teikoku Chemical Industry) and 50 parts of cresol novolac type epoxy resin YDCN703 (manufactured by Toto Kasei) were used. Parts by weight, resol type phenolic resin
2181 (manufactured by Hitachi Chemical) 10 parts by weight, 3 parts by weight of dicyandiamide as a curing agent, SU of polyamideamine
2 parts by weight of NMIDE # 330 (manufactured by Sanwa Chemical Industry Co., Ltd.).
(Showa Denko) 3 parts by weight, Aerosil 200 of silicon oxide
3 parts by weight (manufactured by Nippon Aerosil Co., Ltd.) were dissolved and dispersed in methyl ethyl ketone to obtain a solution having a nonvolatile content of 25%. Using a ball mill, this solution was sufficiently dispersed with an inorganic filler to obtain an adhesive solution.

(2) Preparation of Adhesive Film Both sides of a high-quality paper having a thickness of 130 μm are treated with polypropylene and then an alkyd-based release agent is used. The adhesive is dried so that the thickness of the adhesive becomes 25 μm. Apply the solution,
It was dried at 90 ° C. for 3 minutes in a hot air drier to obtain an adhesive film.

(Evaluation of Properties) (3) Thermal shock test Six rolled copper foils of 35 μm and five adhesive films of 25 μm were alternately sandwiched, and a total of 11 foils were laminated so that the outermost surfaces were all copper foils. Using a vacuum press, press-bonding at 170 ° C. under a pressure of 1 MPa for 3 minutes,
A test piece cured at 150 ° C. for 2 hours was punched out from a circle having a diameter of 3 mm, and was −65 ° C. × 30 minutes, room temperature × 30 seconds, 125 ° C. ×
A thermal shock test was performed for 1 minute at room temperature for 30 seconds for 30 minutes. Observation was performed every 50 cycles, and the number of cycles until cracks occurred at the punched edge was measured. (4) Flowability A 30 mm diameter circle was punched out on a test piece having an adhesive film sandwiched between two 35 μm rolled copper foils, pressed at 170 ° C. under a pressure of 10 MPa for 3 minutes and pressed from the end. The amount of run-off was observed. (5) Reflow soldering heat resistance An adhesive film is sandwiched between two 30 μm rolled copper foils,
Using a vacuum press, press temperature 170 ° C, pressure 1MP
a, After heating and pressing for 3 minutes, the test piece cured after 2 hours at 150 ° C. was left for 12 hours in a humidified condition (temperature of 40 ° C., temperature of 80%) in accordance with JIS C 6481 to obtain a reflow soldering apparatus (Nihon Pulse Co., Ltd.). Using a laboratory (RF430), the test piece was heated so that the sample surface maximum temperature was 260 ° C., and the presence or absence of blisters in the adhesive layer was observed.

Example 2 The procedure of Example 1 was repeated, except that 2 parts by weight of SUNMIDE # 330 of polyamidoamine was 0.1 part by weight of Adeka Hardener EH-285P (Asahi Denka Kogyo KK). went.

Example 3 Example 1 was repeated except that Adeka Hardener EH-285P was changed to 4.0 parts by weight.
Performed in the same manner as in Example 1.

(Comparative Example 1) The procedure of Example 1 was repeated, except that 2 parts by weight of SUNMIDE # 330 of polyamidoamine was not used.

Comparative Example 2 Comparative Example 1 was repeated except that 3 parts by weight of dicyandiamide was changed to 1 part by weight.
The same was done.

Comparative Example 3 Comparative Example 1 was conducted in the same manner as in Comparative Example 1, except that 3 parts by weight of Aerosil 200 was changed to 1 part by weight.
The same was done.

[0033]

[Table 1]

[0034]

The adhesive composition and adhesive film of the present invention are excellent in thermal shock resistance and press workability and are useful as an adhesive for FPC lamination.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05K 1/03 610 H05K 1/03 610H 3/46 3/46 T (72) Inventor Junichi Kotani Noda, Chiba 200, Nakazato, Ichida Noda Plant, Hitachi Chemical Polymer Co., Ltd. (72) Inventor Hisae Ohba 200, Nakazato, Noda City, Chiba Prefecture Hitachi Chemical Co., Ltd.Noda Plant, No. 72 (72) Inventor Hisao Matsumiya 200, Nakazato, Noda City, Chiba Prefecture F-term at Hitachi Chemical Polymer Co., Ltd. Noda Factory (reference) 4J004 AA02 AA10 AA12 AA13 AA16 AA17 AB05 BA03 DA03 DA04 DA05 DB03 DB04 FA05 GA01 4J040 DF041 DF051 EB051 EC021 EC061 EC071 EC091 EC131 EC171 EC261 GA07 HC13 GA05 HC08 HC16 HC23 HC24 HD22 HD39 JA09 JB02 KA14 KA16 LA06 LA08 MA10 MB03 NA20 5E346 AA12 AA16 CC02 CC08 CC32 DD02 DD1 2 EE01 GG02 GG28 HH18 HH31

Claims (3)

[Claims] 1. An acrylic rubber (a) containing a carboxylic acid as a functional group, an epoxy resin (b), a polyamidoamine (c), a phenol resin (d), a curing agent or a curing catalyst (e). Adhesive composition for laminating flexible printed wiring boards. 2. The adhesive for laminating a flexible printed wiring board according to claim 1, wherein the amount of the component (c) is 0.1 to 10 parts by weight based on 100 parts by weight of the component (b). Composition. 3. An adhesive film for laminating a flexible printed wiring board obtained by laminating an adhesive film layer using the adhesive composition according to claim 1 and a release paper.